1. Field of the Invention
The present invention relates to corrosion inhibitors containing both nitrogen and sulfur, in particular the present invention concerns the method of inhibiting corrosion with thio substituted quaternary ammonium salts.
2. Related Art
Nitrogen containing compounds are known to act as corrosion inhibitors, for example, various amines are effective to inhibit corrosion. A number of patents illustrate corrosion inhibitors containing sulfur and/or nitrogen, e.g., sulfur--U.S. Pat. Nos. 3,809,655, 3,759,956, 3,755,176, 3,158,476, 2,880,180, 3,404,094, 3,197,403, 3,969,414; nitrogen--U.S. Pat. Nos. 3,445,441, 3,450,646, 3,976,593; sulfur and nitrogen--3,414,521, 4,450,138.
U.S. Pat. No. 4,450,138 for example, discloses among other reactions, the reaction of thiols with epichlorohydrin followed by the reaction with amines to produce compounds of the general structure: ##STR2## The presence of the hydroxy group would tend to detract from corrosion inhibition based on the analogous compositions prepared by reacting a base amine and alkoxylate which decreases the performance of the quaternary amine compound compared to hydrogen radical being the substituent. U.S. Pat. No. 3,271,443 also discloses alkylamino-2 hydroxypropyl quaternary ammonium compounds including sulfide linkages to form bisquaternary ammonium compounds which are used in halide photographic emulsions as sensitizers.
The synthesis of sulfide compounds of the general formula: EQU R--.sup.+ N(--CH.sub.3).sub.2 CH.sub.2 CH.sub.2 SH Br.sup.-
is disclosed by Anoardi, et al, Functional Micellar Catalysis, Synthesis and Properties of Thiocholine - Type Surfactants, Gazzetta Chimica Italiana, 108, 1978, pg. 707-708, Societa Chimica Italiana as does Moss, et al. A Critical Concentration for Micellar Diastereoselectivity, Tetrahedron Letters, Vol. 24, No. 26, pg. 2615-2618, 1983.
However, there is no mention in this prior art of the thio substituted quaternary ammonium salts per se, i.e., those not substituted with other groups such as OH, as having corrosion inhibiting properties.